LaserJet Pro MFP M277dw won't print envelope

[ForthOK]

Whenever I try to print an envelope using either the manual feed (front slot) or tray 2, the envelope goes through the printer but comes out blank. Then the printer says "Cleaning" for a while. After that it says "Unexpected paper size. Load Letter in tray #x." (where x is the original feed tray number 1 or 2).  Why would it ask for Letter? I have the paper size set exactly to the envelope size in the printer settings as a custom size. I verified that the custom size IS selected. THIS USED TO WORK but now it does not. And yes, I followed the directions in the documentation for printing envelopes. 

[ShlomiL]

Hi,

Have you set the proper size for the printer itself as well?

When loading the envelope, follow the prompt on the screen to change the paper size, or go to Setup > System Setup > Paper Tray Settings and select the correct paper size for the used tray, then try printing the envelope again.

Shlomi

[ForthOK · Accepted solution]

Problem solved: The setting is IN the printer and not accessible from the printer settings on the Mac. You have to open the printer's web browser. On the System tab, select Paper Setup and make sure the paper size for both trays is set to "Any Size." If not, the printer itself enforces page size. Mine was set to Letter so it rejected the envelope as not being Letter size.